Dynamic Response Characteristics And Deformation Mechanism Of Foundation Of Taijiao High-speed Railway Above The Mine-out Areas

With the increasing of the construction density of the "eight horizontal and eight vertical" railway network of China,some high-speed railway lines have to cross the mined-out areas,and infrastructure construction on the goaf site has become an inevitable trend.Therefore,the study of dynamic response and deformation mechanism of the foundation in the mined-out area under the action of dynamic load of high-speed railway has important theoretical significance and engineering practical value for the potential risk control of accumulated deformation along the high-speed railway.Taking the Taijiao high-speed railway crossing the coal mining area of Dianshang as engineering background,the dimensional effect of the foundation scaling model was analyzed and verified according to the energy attenuation theory and the energy transfer law of the soil interface.Based on Winkle foundation beam model theory,a coupled deformation mechanics model of foundation settlement and track structure is established,which reveals the intrinsic relationship between uneven settlement of the foundation and the deformation of track structure.The dynamic response characteristics of goaf foundation under different train working conditions were analyzed by using indoor similar model test and numerical simulation.Combined with the DIC three-dimensional optical digital speckle system,the structural evolution characteristics and migration law of the rock strata of the foundation were analyzed.The prediction model of the cumulative deformation of the foundation of the mined-out area under long-term dynamic loading was constructed,and the damage evolution characteristics and cumulative deformation mechanism of the goaf foundation were revealed.The main research results are as follows:(1)Based on the energy attenuation characteristics of the layered foundation,a dissipation factor that comprehensively represents the kinetic energy of foundation was proposed through theoretical analysis and numerical simulation,and the relationship between the energy attenuation coefficient in layered foundation and the model scale was constructed.At the same time,according to the nonlinear relationship among the energy attenuation coefficient,the model scale,the load,and the vibration frequency,and two-factor equation of the energy attenuation coefficient of the scale model foundation was constructed,and the reliability of the theoretical and numerical simulation results is verified by the indoor scale model.(2)Based on the Winkle foundation beam theory,a coupled deformation mechanics model of foundation settlement and track structure was constructed.A three-dimensional refined numerical model of the foundations in the under-lying mining area of high-speed railways was established by using the displacement boundary and considering inter-layer contact.The coordinated deformation characteristics,spatiotemporal evolution mechanism and the interlayer separation law under different wavelengths and amplitudes of uneven settlement of the foundation were analyzed.The curvature radius was proposed to comprehensively characterize the separation phenomenon between the track structure and the subgrade,and the coupling mapping relationship between the residual deformation of the foundation of the mined-out areas and the geometric deformation of the track structure was revealed.(3)A method of load design of operating condition waveform of high-speed railway was proposed,and the moving load subroutine in numerical simulation was compiled developed.The finite element software Abaqus was used to simulate the dynamic response characteristics of foundation under long-term train dynamic load,the dynamic response distribution characteristics of goaf foundation under different train operating conditions were analyzed and verified by indoor model test.The diffusion mechanism of dynamic stress of the foundation of the mined-out area was revealed.(4)The similar model test and numerical simulation were carried out by using the self-developed similar model combination test bench and electro-hydraulic servo excitation control system.The migration of overlying rock during coal seam mining and the cumulative deformation of the foundation of the mined-out areas under long-term train dynamic loads were analyzed.A cumulative deformation prediction model considering the damage evolution of the foundation was constructed.In addition,a rainfall device was supplemented to the indoor model to reveal the deformation mechanism of the foundation of the mined-out area under the coupling of rainfall and dynamic load.(5)Based on the instability theory of fractured rock mass and the mutation theory of composite beam,a mechanical analysis model of the foundation of the mined-out area was established,and the evaluation basis of the instability of the fractured rock mass and layered composite beam of the foundation was proposed.The DIC monitoring equipment and Image J image processing software were used to extract and analyze the evolution characteristics of the overburden structure of the mined-out area in the indoor physical similarity model,and the structural failure forms of the foundation soil layer of the mined-out area under different load and rainfall stages were obtained,revealing the evolution law of the rock layer structure of the goaf foundation under the coupling effect of long-term dynamic load and rainfall.This paper contains 118 pictures,22 tables,174 references.